A common surgical objective is to avoid unintentional injury to the patient. Oftentimes the anatomical structures (e.g., tissues, organs, vessels, etc.) of interest are surrounded by fatty tissue and other non-target anatomical structures. These objects can obscure the field of view of the surgeon and thus increase the difficulty of identifying the anatomical structures of interest.
Other factors may further complicate this task. In laparoscopic procedures, for example, a three-dimensional space is shown to the surgeon on a two-dimensional display, thereby distorting depth perception and location measurements. Furthermore, even in successful surgical procedures, the surgical site is oftentimes submerged in blood, making it difficult to distinguish between different anatomical structures. In surgical procedures having an obstructed field of view, a surgeon must rely on his or her anatomical knowledge and/or trial-and-error to locate the anatomical structures of interest.
Once the target anatomical structure(s) are identified, it may still be necessary to avoid contact with non-target anatomical structures to prevent unintended injury to the patient. Avoiding contact with non-target anatomical structures can be difficult for reasons similar to those discussed above. Accordingly, identifying anatomical structures of interest and avoiding contact with non-target anatomical structures is oftentimes very difficult and may depend largely on the skill and experience of the surgeon.
Unintentional injury to non-target anatomical structures can result in serious complications during the surgical procedure, increasing both morbidity and mortality rates. Thus, a need exists for the ability to spatially locate surgical instruments and other medical devices relative to anatomical structures and/or other medical devices.
One common unintentional injury associated with open and/or laparoscopic surgeries is injury to the ureter. Ureteral injuries often occur during abdominal surgical procedures such as obstetrics/gynecology (OB/GYN) procedures, colorectal procedures, and urology procedures. Recent studies have found that ureteral injury occurs in up to 2.0% of hysterectomies. Since up to 700,000 hysterectomies are performed in the United States on an annual basis, the number of unintentional ureteral injuries is significant.
To avoid unintentional injury to a non-target anatomical structure, it is helpful to know the location of the non-target anatomical structure. The ureter is surrounded by peritoneal tissue and other vessels that run roughly parallel to the ureter. As a result, the ureter is sometimes mistaken for other vasculature in its vicinity. In complicated cases, there may be scar tissue, tumoral masses, and/or other obstructions that increase the difficulty of identifying the ureter. Successful patient outcomes are therefore largely dependent on the surgeon's knowledge, skill, and familiarity with the surgical procedure. Ureteral injuries, if not detected during surgery, may result in serious complications including formation of ureterovaginal fistulas and potential loss of kidney function.
In some cases, a surgeon may employ one or more medical devices to help identify the location of the ureter. For instance, as preliminary step, a surgeon may insert a simple stent into the ureter. Subsequently, the rigidity of the stent allows the surgeon to feel for the ureter by hand. However, this method is only useful in open surgeries, where the surgeon can freely feel around the surgical area.
Some known ureteral stents integrate a lighting system that extends down the body of the stent and which can shine light through tissue for marking the location of the ureter. However, the light may be difficult to see in certain patients and generally is visible only through a limited layer of obstruction. Furthermore, the increased width and rigidity of lighted ureteral stents makes their insertion difficult and can deform the natural orientation of the ureter. This may render the ureter more prone to injury. Lighted ureteral stents are also significantly more expensive than unlighted ureteral stents.
Other visualization systems, such as infrared mapping systems or biochemically engineered dyes, may be used to locate the ureter. However, these systems typically require expensive equipment, as well as extra training, preparation, and maintenance.
To summarize, unintentional contact and injury to non-target anatomical structures occur in a wide variety of surgeries. Accordingly, a need exists for improved devices, methods, and systems for determining the location of surgical instruments and other medical devices relative to target and non-target anatomical structures.